GENERAL NAVIGATION
HANDBOOK
COMPILED BY: AKSHEY SOOD
, DIRECTION, LATITUDE & LONGITUDE
The Shape of the EARTH
1. Commonly described as an oblate spheroid, that is, a sphere
which is slightly flattened at its poles.
2. The flattening is called compression and in the case of the Earth
is approximately 0.3% (1/300th).
3. The Earth’s polar diameter is 27 Statute miles (or 23 nautical
miles or 43 km) less than its equatorial diameter.
4. Shape of the earth :- Geoid
5. ICAO has adopted world Geodetic System standard 1984.( WGS
84 )
6. For Calculation basis, we considered the earth a true sphere.
THE POLES
1. The Poles are defined as the extremities of the axis about which
the Earth spins.
2. The axis of the Poles is inclined to the axis of the Earth’s orbit
around the Sun at an angle of 23½°.
BASIC DIRECTION ON THE EARTH
1. Cardinal Points :- North, South, East and West
2. Quadrantal directions :- NE, SE, SW,NW
3. When viewed from above the North Pole, the Earth appears to
rotate in an anticlockwise direction.
4. When viewed from above the South Pole, the Earth appears to
rotate in a clockwise direction.
To achieve the required precision, air navigation terminology
retains the cardinal points as a reference but uses the
Sexagesimal system for measuring directions.
SEXAGESIMAL SYTEM/ TRUE DIRECTION
1. The Sexagesimal system utilizes the fact that a clockwise rotation
of direction from North through East, South and West and back to
North is a circle of 360 degrees.
2. the use of 000° or 360° for North is a personal choice (but a
northerly runway would be labeled ‘36’).
3. When the North datum is the direction of the North geographic
pole, it is referred to as True direction. The abbreviation (T) is
used,
4. A 3-figure group is always used - 000°(T), not 0°(T)
5. Runway Directions are normally given with reference to Magnetic North, not True North.
AKSHEY SOOD
,Reciprocal directions :- The direction which is 180° opposite to the direction given.
060 (T) +180= 240 (T)
Position On the Earth /Position Reference System
1. Position Reference System which defines position accurately and unambiguously on the
Earth’s surface.
2. On a plane surface (such as graph paper), position can be defined accurately and
unambiguously using Cartesian co-ordinates ±x and ±y from 2 mutually perpendicular axes
3. The Cartesian system works well on a flat surface but must be modified to work on a
spherical surface, i.e. the Earth
4. The linear co-ordinates x and y are replaced by angular coordinates known as Longitude
and Latitude.
CIRCLES ON THE EARTH
Great Circle
1. A circle on the surface of the Earth whose centre and radius are those of the Earth itself is
called a Great Circle.
2. It is called ‘great’ because a disc cut through the Earth in the plane of the Great Circle
would have the largest area that can be achieved.
3. The shortest distance between two points on the Earth’s surface is the shorter arc of the
Great Circle joining the two points.
4. Given two points on the Earth’s surface, there will be only one Great Circle joining them
(unless the points are diametrically opposed).
THE EQATOR
1. The Great Circle whose plane is at 90° to the axis of rotation of the Earth (the polar axis) is
called the Equator.
2. It lies in an East-West direction and divides the Earth equally into two hemispheres.
3. Equator is the datum for defining Latitude and is the equivalent of the X axis of the
Cartesian system.
The Meridians
1. Meridians are semi-Great Circles joining the North and South poles.
AKSHEY SOOD
, 2. All meridians indicate True North-South direction.
3. Every Great Circle passing through the poles forms a meridian
and its Anti-meridian.
4. The meridians cross the Equator at 90°.
The Prime (or Greenwich) Meridian
1. The meridian passing through Greenwich is known the Prime
Meridian .
2. The Prime Meridian is the datum for defining Longitude and is
the equivalent of the Y axis of the Cartesian system.
Small Circle A circle on the surface of the Earth whose centre and radius are not those of the
Earth is called a Small Circle.
Parallels of Latitude
1. The parallels of latitude are small circles on the surface of the
Earth whose planes are parallel to the Equator.
2. They lie in an East-West direction.
3. Their function is to indicate position North or South of the
Equator.
GRATICULE
1. The network formed on a map or the surface of a globe
by the Prime Meridian, the meridians, the Equator and
the parallels of latitude is called the Graticule.
2. The graticule is an analogy on the Earth’s surface of the X
- Y grid on graph paper
3. Using the graticule the position of any point can be
accurately and unambiguously defined. however, position
is defined by angular measurement(degrees ,minutes &
seconds of arc), not by distance as on cartesian co-
ordinates.
4. This is the foundation of the latitude/longitude.
Angular Measurements
1. The fundamental unit of angular measurement is the degree (°).
2. Which is defined as the angle subtended at the centre of a circle
by an arc equal to the 360th part of the circumference (hence
360° in a circle).
Latitude (Geocentric Latitude)
1. The latitude of any point is the arc (angular distance) measured along the meridian
through the point from the Equator to the point.
2. Latitude is termed north if place is north of equator and south if place is south of equator.
AKSHEY SOOD
HANDBOOK
COMPILED BY: AKSHEY SOOD
, DIRECTION, LATITUDE & LONGITUDE
The Shape of the EARTH
1. Commonly described as an oblate spheroid, that is, a sphere
which is slightly flattened at its poles.
2. The flattening is called compression and in the case of the Earth
is approximately 0.3% (1/300th).
3. The Earth’s polar diameter is 27 Statute miles (or 23 nautical
miles or 43 km) less than its equatorial diameter.
4. Shape of the earth :- Geoid
5. ICAO has adopted world Geodetic System standard 1984.( WGS
84 )
6. For Calculation basis, we considered the earth a true sphere.
THE POLES
1. The Poles are defined as the extremities of the axis about which
the Earth spins.
2. The axis of the Poles is inclined to the axis of the Earth’s orbit
around the Sun at an angle of 23½°.
BASIC DIRECTION ON THE EARTH
1. Cardinal Points :- North, South, East and West
2. Quadrantal directions :- NE, SE, SW,NW
3. When viewed from above the North Pole, the Earth appears to
rotate in an anticlockwise direction.
4. When viewed from above the South Pole, the Earth appears to
rotate in a clockwise direction.
To achieve the required precision, air navigation terminology
retains the cardinal points as a reference but uses the
Sexagesimal system for measuring directions.
SEXAGESIMAL SYTEM/ TRUE DIRECTION
1. The Sexagesimal system utilizes the fact that a clockwise rotation
of direction from North through East, South and West and back to
North is a circle of 360 degrees.
2. the use of 000° or 360° for North is a personal choice (but a
northerly runway would be labeled ‘36’).
3. When the North datum is the direction of the North geographic
pole, it is referred to as True direction. The abbreviation (T) is
used,
4. A 3-figure group is always used - 000°(T), not 0°(T)
5. Runway Directions are normally given with reference to Magnetic North, not True North.
AKSHEY SOOD
,Reciprocal directions :- The direction which is 180° opposite to the direction given.
060 (T) +180= 240 (T)
Position On the Earth /Position Reference System
1. Position Reference System which defines position accurately and unambiguously on the
Earth’s surface.
2. On a plane surface (such as graph paper), position can be defined accurately and
unambiguously using Cartesian co-ordinates ±x and ±y from 2 mutually perpendicular axes
3. The Cartesian system works well on a flat surface but must be modified to work on a
spherical surface, i.e. the Earth
4. The linear co-ordinates x and y are replaced by angular coordinates known as Longitude
and Latitude.
CIRCLES ON THE EARTH
Great Circle
1. A circle on the surface of the Earth whose centre and radius are those of the Earth itself is
called a Great Circle.
2. It is called ‘great’ because a disc cut through the Earth in the plane of the Great Circle
would have the largest area that can be achieved.
3. The shortest distance between two points on the Earth’s surface is the shorter arc of the
Great Circle joining the two points.
4. Given two points on the Earth’s surface, there will be only one Great Circle joining them
(unless the points are diametrically opposed).
THE EQATOR
1. The Great Circle whose plane is at 90° to the axis of rotation of the Earth (the polar axis) is
called the Equator.
2. It lies in an East-West direction and divides the Earth equally into two hemispheres.
3. Equator is the datum for defining Latitude and is the equivalent of the X axis of the
Cartesian system.
The Meridians
1. Meridians are semi-Great Circles joining the North and South poles.
AKSHEY SOOD
, 2. All meridians indicate True North-South direction.
3. Every Great Circle passing through the poles forms a meridian
and its Anti-meridian.
4. The meridians cross the Equator at 90°.
The Prime (or Greenwich) Meridian
1. The meridian passing through Greenwich is known the Prime
Meridian .
2. The Prime Meridian is the datum for defining Longitude and is
the equivalent of the Y axis of the Cartesian system.
Small Circle A circle on the surface of the Earth whose centre and radius are not those of the
Earth is called a Small Circle.
Parallels of Latitude
1. The parallels of latitude are small circles on the surface of the
Earth whose planes are parallel to the Equator.
2. They lie in an East-West direction.
3. Their function is to indicate position North or South of the
Equator.
GRATICULE
1. The network formed on a map or the surface of a globe
by the Prime Meridian, the meridians, the Equator and
the parallels of latitude is called the Graticule.
2. The graticule is an analogy on the Earth’s surface of the X
- Y grid on graph paper
3. Using the graticule the position of any point can be
accurately and unambiguously defined. however, position
is defined by angular measurement(degrees ,minutes &
seconds of arc), not by distance as on cartesian co-
ordinates.
4. This is the foundation of the latitude/longitude.
Angular Measurements
1. The fundamental unit of angular measurement is the degree (°).
2. Which is defined as the angle subtended at the centre of a circle
by an arc equal to the 360th part of the circumference (hence
360° in a circle).
Latitude (Geocentric Latitude)
1. The latitude of any point is the arc (angular distance) measured along the meridian
through the point from the Equator to the point.
2. Latitude is termed north if place is north of equator and south if place is south of equator.
AKSHEY SOOD
